Biology subjects

Sandry, J.

Publications and source records attributed to Sandry, J..

3 recordsLinked to original sources

bioRxiv2025

Resting-state Functional Connections with the Hippocampus and with the Caudate Nucleus Predict Working Memory Performance in Multiple Sclerosis

Episodic memory (EM) dysfunction is a common symptom of multiple sclerosis (MS). A related process, working memory (WM), supports long-term EM and is often also impaired. Functional connectivity (FC) between the hippocampus and caudate nucleus supports EM performance. However, this connectivitys specific influences on WM performance in MS is relatively unknown. Resting-state FC (RSFC) possesses clinical utility, including predicting cognitive impairments before they are captured by assessment. The present study tested whether RSFC with the hippocampus and caudate could predict WM performance in people with MS and in healthy individuals (HC). In a secondary analysis of 78 participants (42 MS, 36 HC), RSFC between the hippocampus, caudate nucleus, and other regions was quantified. These connections predictive influence on WM performance was then examined using a global WM performance measure for a subset with available neuropsychological data (26 MS, 15 HC). Across the entire sample (N=78), MS participants displayed stronger coupling between the right hippocampus and left dorsomedial prefrontal cortex, compared to HC participants. Within MS participants, stronger coupling between the left hippocampus (LHipp) and left ventral anterior cingulate (LvACC), and between the left caudate (LCaud) and right insula, were observed. Stronger decoupling between the LHipp and left supramarginal gyrus (LSMG) also emerged. Stronger LHipp-LvACC connectivity predicted worse WM performance, whereas stronger LHipp-LSMG connectivity and LCaud-RInsula connectivity each predicted better performance. The hippocampal connections were also inversely correlated. Findings identify a caudate circuit and potential hippocampal network whose aberrant, intrinsic activity could serve as neural markers for WM dysfunction in MS.

neuroscience↗

bioRxiv2023

Bypassing Striatal Learning Mechanisms Using Delayed Feedback to Circumvent Learning Deficits in TBI

ObjectiveFeedback facilitates learning by guiding and modifying behaviors through an action-outcome contingency. As the majority of existing studies have focused on immediate presentation of feedback, the impact of delayed feedback on learning is understudied. Prior work demonstrated that learning from immediate and delayed feedback employed distinct brain regions in healthy individuals, and compared to healthy individuals, individuals with traumatic brain injury (TBI) are impaired in learning from immediate feedback. The goal of the current investigation was to assess the effects of delayed vs. immediate feedback on learning in individuals with TBI and examine brain networks associated with delayed and immediate feedback processing. SettingNon-profit research organization. ParticipantsTwenty-eight individuals with moderate-to-severe TBI. DesignParticipants completed a paired-associate word learning task while undergoing MRI. During the task, feedback was presented either immediately, after a delay, or not at all (control condition). Main measuresLearning performance accuracy; confidence ratings; post-task questionnaire, blood-oxygen-level dependent signal. ResultsBehavioral data showed that delayed feedback resulted in better learning performance than immediate feedback and no feedback. In addition, participants reported higher confidence in their performance during delayed feedback trials. During delayed vs. immediate feedback processing, greater activation was observed in the superior parietal and angular gyrus. Activation in these areas has been previously associated with successful retrieval and greater memory confidence. ConclusionThe observed results might be explained by delayed feedback processing circumventing the striatal dopaminergic regions responsible for learning from immediate feedback that are impaired in TBI. Additionally, delayed feedback evokes less of an affective reaction than immediate feedback, which likely benefited memory performance. Indeed, compared to delayed feedback, positive or negative immediate feedback was more likely to be rated as rewarding or punishing, respectively. Findings have significant implications for TBI rehabilitation and suggest that delaying feedback during rehabilitation might recruit brain regions that lead to better functional outcomes.

neuroscience↗

bioRxiv2022

ALFF Response Interaction With Learning During Feedback in Individuals With Multiple Sclerosis

Amplitude of low-frequency fluctuations (ALFF) is defined as changes of BOLD signal during resting state (RS) brain activity. Previous studies identified differences in RS activation between healthy and multiple sclerosis (MS) participants. However, no research has investigated the relationship between ALFF and learning in MS. We thus examine this here. Twenty-five MS and 19 healthy participants performed a paired-associate word learning task where participants were presented with extrinsic or intrinsic performance feedback. Compared to healthy participants, MS participants showed higher local brain activation in the right thalamus. We also observed a positive correlation in the MS group between ALFF and extrinsic feedback within the left inferior frontal gyrus, and within the left superior temporal gyrus in association with intrinsic feedback. Healthy participants showed a positive correlation in the right fusiform gyrus between ALFF and extrinsic feedback. Findings suggest that while MS participants do not show a feedback learning impairment compared to the healthy participants, ALFF differences might suggest a general maladaptive pattern of task unrelated thalamic activation and adaptive activation in frontal and temporal regions. Results indicate that ALFF can be successfully used at capturing pathophysiological changes in local brain activation in MS in association with learning through feedback.

neuroscience↗